An analysis of the technical problems involved indicates that the use of lasers in the vascular system remains a complex problem, but one that is eminently approachable with continued research. The emphasis should be on continued basic research rather than on the accumulation of large clinical experiences with less than adequate technology. There is great potential for the development of a percutaneous treatment for coronary artery disease that may reduce restenosis rates compared to those seen with percutaneous transluminal balloon angioplasty. Development of an effective percutaneous treatment of coronary artery disease with long term durability is critical to the advancement of interventional cardiology.

Excess free radical production is known to cause tissue injury in a number of contexts such as coronary reperfusion, atherosclerosis, and lipopolysaccharide-induced endothelial cell injury. Free radicals have proved to be difficult to measure in vivo due to their low concentrations and short lifetime. Because free radicals readily oxidize lipoproteins, we propose to assess free radical production using the degree of oxidation of circulating lipoproteins as an index. An advantage of using oxidized lipoproteins as an indicator of free radical activity is that their half-lives in plasma are extremely long (minutes to hours depending on the extent of oxidation). In addition oxidized low density lipoprotein (o-LDL) has been shown to be toxic to various cells1 and is believed to be present in atherosclerotic plaques.2,3 Its level in plasma therefore may itself be an Important determinant of tissue damage. It has been demonstrated that when LDL is oxidized in vitro, its fluorescence emission spectrum is significantly altered.4 We measured LDL and o-LDL spectra in a fluorimeter with an excitation wavelength of 365 nm.

Successful recanalization of atherosclerotic vessels requires removal of precise amounts of diseased tissue without excessive heating of adjacent healthy tissue or vessel wall perforation. This requirement for controlled ablation necessitates accurate delivery of a prescribed photon dose at the tissue surface. We will describe the engineering and performance of a multifiber laser catheter which achieves this objective.

Laser angiosurgery is a potential powerful method for treating atherosclerosis in coronary and peripheral vessels. Treatment is based on ablating arterial plaque using laser light delivered via a catheter containing fiber optics. From an engineering point of view laser angiosurgery can be viewed as a problem in controlled tissue matching and can be attacked using the tools of spectroscopy and physics.

A group of 408 catheterised patients who had mild angina or myocardial infarction without angina was selected in conformity with the criteria for entry into a previously reported randomised trial. Medical treatment had been chosen initially by the cardiologist, referring physician, or the patient, although 27% had late operation. Five year survival rates were 91% and 72% for mild angina with high or low ejection fractions and 85% for those who had myocardial infarction without subsequent angina. Survival rates were 95%, 88%, and 80% for one, two, and three artery disease respectively. For patients who had ejection fractions of at least 0.50, five year survivals were 95%, 89%, and 83% for one, two, and three artery involvement respectively. Good left ventricular function, single artery disease, and a short history were favourable prognostic variables in multivariate analysis of patients who had angina pectoris. Statistical methods of dealing with patients who had late operation influenced calculated survival, especially for patients at relatively high risk. The lower survival rates for the whole group and most subsets compared with survival rates in the randomised trial may be of clinical importance.

Controlled delivery of light is necessary for the precise removal of tissue in laser angiosurgery. We describe an optical fiber laser catheter incorporating a transparent, protective optical shield which provides such control. Tissue removal data characterizing the performance of the device are presented.

To evaluate the sensitivity and specificity of two-dimensional echocardiography for the detection of left main coronary artery disease, echocardiograms were obtained of 47 patients (38 men and 9 women) with the use of a Hewlett-Packard phase array system. Coronary arteriograms were also obtained. Three falsepositive results compared with 28 true-positive cases resulted in a specificity of 90% for two-dimensional echocardiography; 3 patients had normal echocardiograms in the presence of significant angiographic lumen narrowing. Since 9 patients had left main trunk disease, sensitivity was 67%. Our findings suggest that twodimensional echocardiography is somewhat limited in permitting visualization of left main coronary artery disease.

This study reviews data on 107 patients, aged 35 years or younger, who underwent surgical coronary revascularization from 1971 to 1975. Early clinical events included one operative death and five nonfatal perioperative myocardial infarctions. Late follow-up (mean interval after operation 115 months) demonstrated actuarial survival rates of 94% at 5 years and 85% at 10 years. Fifteen late deaths, 23 nonfatal myocardial infarctions, 13 reoperations and return of severe angina in 10 patients were considered late clinical events. Actuarial survival free of early or late clinical events was 77% at 5 years and 53% at 10 postoperative years. Testing of clinical, angiographic and operative variables for influence on survival and event-free survival showed that survival was decreased by multivessel disease and impaired left ventricular function; event-free survival was decreased by a family history of coronary disease and cigarette smoking. Both survival and event-free survival were decreased by diabetes and elevated serum cholesterol. Postoperative cardiac catheterization (64 patients, mean postoperative interval 47 months) demonstrated that mammary artery graft patency (25 of 27, 93%) exceeded vein graft patency (49 of 88, 56%, p less than 0.01). The atherogenic diatheses of young adults may compromise the operative result, whereas use of internal mammary artery grafts may enhance the palliation of bypass surgery.